As shown in FIG. 1, a wireless communication system 10 comprises elements such as client terminal or mobile station 12 and base stations 14. Other network devices which may be employed, such as a mobile management entity, are not shown. In some wireless communication systems there may be only one base station and many client terminals while in some other communication systems such as cellular wireless communication systems there are multiple base stations and a large number of client terminals communicating with each base station.
As illustrated, the communication path from the base station (BS) to the client terminal direction is referred to herein as the downlink (DL) and the communication path from the client terminal to the base station direction is referred to herein as the uplink (UL). In some wireless communication systems the client terminal or mobile station (MS) communicates with the BS in both DL and UL directions. For instance, this is the case in cellular telephone systems. In other wireless communication systems the client terminal may communicate with the base stations in only one direction, usually the DL. This may occur in applications such as paging.
The base station with which the client terminal is communicating is referred to as the serving base station. In some wireless communication systems the serving base station may be referred to as the serving cell. The terms base station and a cell may be used interchangeably herein. A cell from which a client terminal has already received service may be referred to as having visited that cell. In general, the cells that are in the vicinity of the serving cell are called neighbor cells. Similarly, in some wireless communication systems a neighbor base station may be referred to as a neighbor cell.
A cell may broadcast the essential information about it to enable the client terminals to get service from it. This essential information about a cell is referred to herein as System Information (SI). The SI may be organized into multiple units of information in the form of different SI messages. An SI message that includes the most frequently used information may be broadcast more frequently and an SI message with less frequently used information may be broadcast less frequently.
A wireless communication network may use multiple Radio Access Technologies (RAT) to provide service. For example, a network may use two or more of the RATs that include but not limited to: the 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), the 3GPP Wideband Code division Multiple Access (WCDMA), Code Division Multiple Access (CDMA), the 3GPP Global System for Mobile (GSM), and the Institute of Electrical and Electronics Engineers (IEEE) 802.16. The coverage area of cells of two or more RATs belonging to the same network may overlap fully, or may overlap partly, or may be disjoint. In some cases the base stations for cells belonging to different RATs may be co-located.
Each base station may be identified by a unique identifier referred to herein as Cell Identity (CID). The CID of a base station may become known to a client terminal when it decodes SI from the base station. The CID may be of different types such as Cell Global Identity (CGI) in case of 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) wireless communication system. A base station may have additional identities such as Closed Subscriber Group (CSG) identity.
When a client terminal is involved in active communication with the network, such as a voice/video call, text messaging, internet browsing, etc., the client terminal may be considered to be in Connected state. When a client terminal is not involved in active communication with the network, it may be considered to be in Idle state. When a client terminal is either in Connected state or in Idle state, it is considered to be receiving service from a cell. For example, in case of Connected state, receiving service may include engaging in a voice call. For example, in case of Idle state, receiving service may include receiving paging messages and/or SI messages. When transitioning from Idle state to Connected state and vice versa, a client terminal may be in some intermediate states. A client terminal periodically makes measurements on the serving cell and its neighbor cells in order to maintain continued service from the best possible cell. When a client terminal is mobile, it may switch from one cell to another to continue to get service. The switch from one cell to another when a client terminal in Connected state is referred to herein as handover. The switch from one cell to another when a client terminal in Idle state is referred to herein as cell reselection.
When a client terminal is in Idle state, it may periodically listen to the network for any paging messages that may be sent by the network, for example, if there is an incoming call for the client terminal. When a client terminal is in Idle state and mobile, it may perform cell reselection. To ensure that it continues to receive service from the network, it may need to inform the network that it has performed the cell reselection and that it is receiving service from a different cell. However, this may be wasteful from both the client terminal and network perspective. This is because most of the time, a client terminal may pass through a cell without ever getting into Connected state in that cell. However, a network may need to be able to reach a client terminal if there is any incoming communication, such as a call, for the client terminal. To avoid the unnecessary updates from the client terminal and yet ensure the ability to reach a client terminal at any given time, the network may organize a group of cells into a “tracking area” and use a Tracking Area Identity (TAI) to identify the various groups of cells. This is illustrated in FIG. 2 where four different tracking areas are illustrated. A cell may broadcast information about the tracking area it belongs to by including the TAI information in the SI. A client terminal may be required to inform the network when it begins to receive service from a cell that belongs to a tracking area that is different from the tracking area of the cells from which it was previously receiving service. The process of informing the network that the client terminal has begun receiving service from a cell that belongs to a new tracking area is referred to herein as Tracking Area Update (TAU) procedure. With this method, a client terminal performs TAU only when there is a change in TAI of the cell from which it is getting service. For example, in FIG. 2, when a client terminal reselects from the cell with CID=1003 to the cell with CID=1007 which has the same TAI, it may not perform TAU procedure. However, when the client terminal reselects from the cell with CID=1007 and TAI=200 to the cell with CID=1012 and TAI=201, it may perform TAU procedure.
Location determination is a commonly available and used capability in many client terminals in wireless communication networks. The terms location determination and positioning are used interchangeably herein. Client terminals may obtain their own location through different technologies. A satellite navigation system with global coverage commonly known as Global Navigation Satellite System (GNSS) and the Observed Time Difference of Arrival (OTDOA) are two example technologies.
In some scenarios, it may be useful for a client terminal to know the location of one or more base stations in a wireless communication network. For example, a client terminal may make decisions about whether to make cell reselection and/or handover related measurements and system information decoding as well as how frequently to look for neighboring base stations based on the location information of the base stations.
While a network may know its location accurately, generally it may not provide that information to a client terminal. Furthermore, the location information for a base station may be required before a client terminal can communicate with the particular base station.